It has been widely practiced to produce a rigid foam by reacting an active hydrogen compound having at least two active hydrogen-containing groups reactive with isocyanate groups, with a polyisocyanate compound in the presence of a catalyst and a blowing agent. As the active hydrogen compound, a polyhydroxy compound or a polyamine compound may, for example, be mentioned. Various compounds are known as blowing agents for producing rigid foams. However, trichlorofluoromethane (R-11) is mainly used. Further, it is common to use water together with R-11. Further, in a case where foaming is conducted by e.g. a floss method, dichlorodifluromethane (R-12) having a lower boiling point (gaseous under atmospheric pressure at room temperature) is used together with them. Further, various proposals have been made to the effect that chlorinated fluorohydrocarbons having relatively low boiling points can be used as blowing agents, but none of them has been widely used except for the above mentioned R-11 and R-12. Further, it has been proposed to use instead of the chlorinated fluorohydrocarbon blowing agents other halogenated hydrocarbon blowing agents having low boiling points, such as methylene chloride.
A chlorinated fluorohydrocarbon which is extremely stable in the atmosphere such as R-11 or R-12 which has been widely used, is believed to reach the ozone layer located at the upper part of the atmosphere without being decomposed and then be decomposed by the action of e.g. ultraviolet rays, and the decomposed product is suspected to destroy the ozone layer. Part of such a chlorinated fluorohydrocarbon used as a blowing agent leaks into the atmosphere. Therefore, it is presumed that its use constitutes part of the cause of the destruction of the ozone layer. Accordingly, it has been required to reduce the amount of use of a blowing agent of such chlorinated fluorohydrocarbon type, or to replace it by other blowing agents.
As other blowing agents, halogenated hydrocarbons having hydrogen atoms, such as chlorinated fluorohydrocarbons having hydrogen atoms or fluorohydrocarbons having hydrogen atoms, have been proposed. However, if a halogenated hydrocarbon having hydrogen atoms is used, the initial strength of the resin during the production of a rigid polyurethane foam tends to substantially decrease, and the properties for a heat shielding material as one of the main uses of the rigid polyurethane foam, tend to be poor. Therefore, it is strongly desired to establish a technique to produce a rigid foam having high performance using a halogenated hydrocarbon having hydrogen atoms.